A New Platform for Designing Ligands for Asymmetric Induction in Allylic Alkylations

Simply inverting the orientation of the amide function as in 1 compared to that of the ligand series derived from 2-diphenylphosphinobenzoic acid affects the enantiomeric discriminating step in the Pd-catalyzed nucleophilic alkylation of meso-1,4-dihydroxy-2-cycloalkenes. In reactions such as this, the bond-making or -breaking event occurs outside the coordination sphere of the metal. The chiral scaffold of the ligand is connected to the metal atom by a linker (here 2-diphenylphosphinoaniline), and the preferred conformation of the catalysts provides “chiral spaces” for the substrate–a conclusion supported by X-ray crystallography.